Direct fired hot water generators such as that shown in U.S. Pat. No. 4,574,775 to Lutzen et al generally have a container wherein water is introduced at the top thereof and falls downwardly through a heat exchange column, with obstacles therein to prevent a straight line path therethrough and having a burner at the bottom thereof for introducing heat and products of combustion which flow upwardly, counter to the flow of the water flowing downwardly, whereby the water is heated by such contact. Flue gases exit the top of the container and the heated water is pumped to where the heat is to be used. After the heat has been utilized, this water is returned to the container and to the inlet therein for re-heating and re-use.
One of the problems with prior art in direct fired hot water generators is that heat is lost in the flue gases which are exhausted to atmosphere. This creates an extremely inefficient situation.
Consequently, there is a need for a direct fired hot water generator which utilizes as much of the heat from a flame as possible.